Lecture 2 - Clincal Trials Flashcards
What is the problem with not having a control group in a study?
Not easy to compare how well a certain treatment works
What is the definition of a clinical trial?
Any form of planned experiment which involves patients and is designed to decide the most appropriate method of treatment for future patients with a given condition
What is the purpose of a clinical trial?
To provide reliable evidence of treatment efficacy and saftey
What are the stages to drug development and monitoring?
Pre clinical phase
Phase 1 = volunteer studies
Phase 2 = treatment studies
Phase 3 = clinical trials
Phase 4 = post marketing surveillance
What is the purpose of phase 3 clinical trials?
Comparison of the new drug with standard a;ready existing treatments
What is the purpose of phase 1 volunteer studies?
Pharmacodynamics
Phhharmacokinetics
Major side effects
What is the purpose of phase 2 treatment studies?
Effects and dosages
Common side effects
What is the purpose of phase 4 post marketing surveillance?
Monitoring for adverse reaction and potential new uses
What are the most importnat ethical considerations for any trial to go ahead?
Trials of new drugs may do harm
The patients must given informed constent so must understand risk involved
What is clinical equipoise?
When we are very unsure on whether a new drug will be more effective if given so we will only know if we trial it
What is a non-randomised clinical trial?
When the way patients are allocated to receive a new treatment versus the standard treatment (the controls) is non random (you chose who gets the treatment)
What is comparison with historical controls in non randomised clinical trials?
All future patients may get new treatment and their outcomes are compared with patients in th least 6 months who were given standard treatment
What is there problem with the historical control group in non-randomised clinical trials?
Selection is often less well defined
Treated differently from new treatment group
Less info on potential con founders
Can control for confoudners
What is the advantages of randomisation for clinical trials?
Minimises affects of confounding
What is a confounded/confounding?
When there is a third factor that is associated with the exposure and the outcome and that distorts the relationship between them
What is a common confounder between alcohol and MI?
Smoking
Since alcohol does increase risk of MI
But if you drink you’re more likely to smoke and smoking increases risk of MI
What are some ways randomisation can be carried out?
Toss a coin
Random number tables
Sequentially numbered sealed envelopes containing the random allocation as participants are recruited
Why is sample size important in a random clinical trial?
Larger sample sizes help reduce the affect of confounding keeping trials as fair as possible
What are the key features for a clinical trial to be fair and safe?
Reproducible
Controlled (intervention and comparison group)
Fair (unbiased without confounding)
What are some possible affects if a patient knows what group they are in in a random clinical trial?
May cause bias:
Performance bias since the patient may alter their behaviour if they know they haven’t received the drug so may seek other treatements or alter their expectations
Information/detection bias since investigator may alter to their approach when making measurements and assessing outcomes
What is a single blind trial?
Usually the patient doesn’t know what group they are in
What is a double blind trial?
Usually two of patient and clinician or assessor doesn’t know which group the patient is in
What is the problem with a recruiter knowing who will receive the new treatment and who wont?
May cause allocation bias since the recruiter will likely want to recruit a person who they think will do better with the new treatment if they know that the next patient will receive the new treatment
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What type of bias is allocation bias?
Selection bias
What is allocation bias?
Where the recruiter knows the allocation process which can lead to them unucoonsciously affect who gets enrolled in the trials
What is the purpose of allocation concealment?
What does it prevent?
To hide hte randomisation sequence from those recruiting people in the trial to prevent allocation bias
What is the purpose of randomisation?
Distributing confoudners equally between groups
What is the purpose of blinding?
Makes patient and clinicians unaware of treatment received to prevent bias on how patients and clincians act
How do we decide who and who shouldn’t participate in a clinical trial?
Using inclusion and exclusion criteria
What are the reasons for pre-defining outcomes in clinical trials?
To prevent data dredging/repeated analysis (randomly finding information that matches what you want)
Have a clear protocol for data collection
Agreed criteria for measurement and assessment of outcomes
What is the primary outcome used to calculate?
Sample size
What is an example of a primary outcome and secondary outcome in a clinical trial?
Primary = death
Secondary = side effects
What are the features of an ideal outcome?
Appropriate and relevant to patient, clinician and society
Valid and attributable to the intervention
Sensitive and specific
Reliable and robust
Simple and sustainabbbble
Cheap and timely
What is a secondary outcome?
Outcomes that are of interest but not primary interest
What is a key feature of being able to compare groups in a random trial?
Need to ensure groups compared are as equivalent as possible
What is the placebo affect?
The therapy may be irrelevant to the patients condition but the patients attitude to their condition may be improved by a feeling that something is being done about it
What is a placebo?
An inert substance made to appear identical in every way to the active formulation with which it is to be compared
What is the aim of a placebo?
To cancel out any placebo effect that may exist in the active treatment
So its clear to see any improvement in patient condition was due to the active treatment working and not the placebo affect
When is a placebo used?
When there is no standard treatment available so the new active treatment needs to have a comparator
What is losses to follow up in clinical trials?
Not every patient remains in the trials
So their condition may require their removal from the trial
May just choose to withdraw
How do we minimise losses to follow up?
Make the follow up practical and minimise inconvenience
Be honest about the commitment required
Maintain contact with participants
Avoid coercion
Why may patients not adhere with treatments?
May have misunderstood the instructions
Can’t be bothered to take treatment
Might not like their treatment
May briefer to take another treatment
How do we maximise treatment adherence?
Simplify instructions
Ask about adherence
Monitor adherence
What is an explanatory trials?
Per protocol analysis
Analyse those who completed follow up and adhered to treatments
Loses effects of randomisation so might introduce confounding
What is a pragmatic trial?
Intention to treat analysis
Analyses ALL according to original allocation to treatment groups regardless of whether they completed follow up or adhered
Preserves effects of randomisation and minimises confounding and bias
What are the advantages or per protocol analysis and then intentional to treat analysis?
Per protocol analyses tend to give larger sizes of effect
Intention to test analyses tend to give smaller and more realistic sizes of effect
What are the 3 key steps in RCT?
Set up (diseases of interest and treatments)
Conduct of trial
Analysis of outcomes
What is PICO?
Population
Intervention
Comparator
Outcome